TRAFFIC LIGHTS

Timaru Herald, Volume CXXXVIII, Issue 19959, 17 November 1934, Page 10

TRAFFIC LIGHTS

A NEW AMERICAN BULB Fatalities have been caused by the burning out of incandescent lamps that illuminate the red lenses of traffic signals, states a report in the American Press. A failure of this sort provides a considerable hazard, especially as the green lenses facing the intersecting highway remain illuminated. The motorist who should be receiving an indication to stop is given no indication at all, while drivers on the intersecting street are being informed that the way is clear. A like hazard is created by failure of the green to show. The approaching driver sees only a dark lens, and assumes that the signal is not in operation. Therefore, he is not alert for any change of indication. As the amber or red light is suddenly flashed on, he makes a sudden stop that is likely to result in a collision with the car behind. To prevent such traffic light failure the Police Department of Baltimore recently installed in 300 signals, a new type of incandescent lamp. It is constructed with two filaments placed parallel with each other and slightly spaced by a central metal screen. Normally, both filaments are incandescent and the entire bulb is illuminated. However, upon the failure of either filament, the screen causes the lamp to be divided into contrasting bright and dark areas. This effect is reproduced on the signal lens and thus gives unmistakable notification that the lamp should be replaced. At the same time illumination is still provided on the bright portion of the lens, enabling the signal to be read clearly by motorists. Patrolmen, motor men, and bus drivers are instructed to reort promptly the location of any signal that gives warning of an impending burn-out by showing a darkened facet. These reports are relayed to the traffic maintenance men, who quickly replace the lamps. For the Colour Blind In recognition of the fact that many motorists are colour-blind, the signals of Baltimore have also been equipped with colour-lenses that can be read by drivers so afflicted. In ,each lens a prismatic band has been moulded, the position of the band being different for each colour. The band in the red lens is horizontal, this position tending to convey the impression of a barrier. The position of the band in the green glass is vertical and creates the effect of progress. The amber signal has a diagonal band, giving a nondirectional impression. Each band is an integral part of the lens, and differs from the remaining area because of its prismatic structure. The bands are clearly distinguishable in the circular lens area for a considerable distance, and pedestrians, viewing signals at an angle, can see them as well as motorists.